Production or exploration wells in the oil and gas industry are provided with one or more well bore control devices, such as a blow out preventer or a riser control device, for sealing the well bore in the event of an emergency in order to protect personnel and the environment. Conventional wellbore control devices have cutting rams mounted perpendicular to a vertical throughbore. The rams can be activated to sever a tubular disposed in the wellbore and to seal the well bore. The cutting rams move through a horizontal plane and are often driven by in-line piston hydraulic actuators.
Such well bore control devices must withstand extreme conditions during use, which sets stringent requirements for their design. In order for the well to be closed and sealed in an emergency, the device must be able to cut anything present in the wellbore, which can be a drilling tubular, casing, or tools for well intervention. Effective sealing is also required against what may be very high wellhead pressures.